Greece made a $222 million interest payment to the International Monetary Fund (IMF) Wednesday. But another, much larger payment looms, and it's not clear if Athens will be able to make it.

Athens is supposed to repay $1 billion to the IMF by May 12. If it defaults on that debt, Greek membership in the the eurozone could be jeopardized.

The left-wing government of Greece has been locked in tough negotiations with its creditors over the issue for several months.

The European Union expressed confidence Tuesday that Greece and its creditors would take necessary steps to keep the country solvent and in the eurozone.

Greek Finance Minister Yanis Varoufakis was in Rome Wednesday to discuss the issue with his Italian counterpart Pier Carlo Padoan. Varoufakis is expected to travel to Madrid on Friday to meet the Spanish finance minister.

International creditors have demanded the Greek government implement economic reforms and budgetary measures before they release more funds from a financial rescue package for Athens.